1. Field of the Invention
The present invention relates generally to the manufacture of glass articles such as bottles and the like, and more particularly, to methods and apparatus for permitting increased productivity in a glass manufacturing process by utilizing flows of pressurized cold cryogen vapor that are introduced into mold cavities to hasten the cooling and solidification of newly molded glass articles.
2. Prior Art
In the molding of glass articles such as bottles and the like, a hollow blank or parison of glass is typically formed in a roughing mold, and is inserted into a finishing mold where it is expanded to form an article of desired form. The hollow blank of glass is typically formed by pressing a gob of glass and/or by using a pressurized flow of ambient air as a blowing gas to conform the gob to a desired configuration. The resulting blank roughly approximates the shape of the final article that is to be molded, but has thicker walls and is smaller in size. The blank is expanded in the finishing mold to conform to a desired configuration as defined by the finishing mold. Expansion of the blank is typically effected by pressing and/or by using a pressurized flow of ambient air as a blowing gas.
In the molding of a preliminary article of glass such as a hollow blank or parison, and in the molding of articles of final form such as bottles, it is not uncommon to utilize flows of cooling gas that are directed toward the newly molded articles while the articles are still contained within their mold cavities to speed cooling and solidification of the articles so they can be removed as quickly as possible from their molds. The cooling gas is typically ambient air that has been pressurized by a blower. The cooling gas is typically fed from a manifold through a control valve and ducted into the mold cavities, with the gas having temperatures that lie within a range of about 90 to 100 degrees Fahrenheit, and sometimes higher. Where the articles being molded have been formed using blow-molding techniques, the blowing gas also typically comprises blower-pressurized ambient air that is ducted into the mold cavities at temperatures that lie within a range of about 90 to 100 degrees Fahrenheit, and sometimes higher. In most applications, the flows of cooling gases are uninterrupted extensions of the flows of blowing gases that are delivered into the mold cavities to blow-form articles therein.
In order to further speed the cooling of molded glass articles to diminish their mold retention times, proposals have been made to indirectly cool the articles by providing at least portions of their molds with cooling passages through which a fluid coolant is circulated. However, the degree to which mold cooling can be used to indirectly cool molded glass articles is limited not only by the tendency of this approach to induce defects (the number of defects induced in molded glass articles increases as mold temperatures are diminished), but also by the cost of forming cooling passages in the molds, and by the cost of providing suitable apparatus for maintaining controlled flows of coolant through the cooling passages.
While mold cooling does provide some assistance in diminishing mold retention times, the retention times during which newly molded glass articles must be held in their molds to effect proper solidification continue to form "bottlenecks" that obstruct efforts to increase the productivity of existing molding equipment.